In prior art, methods are known for preparing weakly or strongly superalkalinized sulfonates from sulfonic acids obtained by the sulfonation of different alkyl aryl hydrocarbons and from an excess of alkaline earth base.
The alkyl aryl hydrocarbons subjected to the sulfonation reaction are obtained by alkylation via the Friedel and Craft reaction of different aryl hydrocarbons, particularly aromatic, with two different types of olefin:
Branched olefins obtained by the oligo-polymerization of propylene to C.sub.15 to C.sub.42 hydrocarbons, particularly the propylene tetrapolymer dimerized to a C.sub.24 olefin, and PA1 Linear olefins obtained by the oligo-polymerization of ethylene to C.sub.14 to C.sub.40 hydrocarbons. PA1 (a) from 50% to 85% of a linear mono-alkyl phenyl sulfonate in which the linear alkyl chain contains between 14 and 40 carbon atoms, and between 0 and 13 mole % of the phenyl sulfonate radical of the alkaline earth metal is fixed on position 1 or 2 of the linear alkyl chain, and PA1 (b) from 15% to 50% of a heavy alkyl aryl sulfonate selected from: PA1 (1) Ashless dispersants: alkenyl succinimides, alkenyl succinimides modified with other organic compounds, and alkenyl succinimides modified with boric acid, alkenyl succinic ester. PA1 (2) Oxidation inhibitors: PA1 (3) Rust inhibitors (Anti-rust agents): PA1 (4) Demulsifiers: addition product of alkylphenol and ethyleneoxide, poloxyethylene alkyl ether, and polyoxyethylene sorbitane ester. PA1 (5) Extreme pressure agents (EP agents): zinc dialkyldithiophosphate (Zn-DTP, primary alkyl type & secondary alkyl type), sulfurized oils, diphenyl sulfide, methyl trichlorostearate, chlorinated naphthalene, benzyl iodide, fluoroalkylpolysiloxane, and lead naphthenate. PA1 (6) Friction modifiers: fatty alcohol, fatty acid, amine, borated ester, and other esters PA1 (8) Viscosity Index improvers: polymethacrylate type polymers, ethylene-propylene copolymers, styrene-isoprene copolymers, hydrated styrene-isoprene copolymers, polyisobutylene, and dispersant type viscosity index improvers. PA1 (9) Pour point depressants: polymethyl methacrylate. PA1 (10) Foam Inhibitors: alkyl methacrylate polymers and dimethyl silicone polymers. PA1 (a) a major amount of an oil of lubricating viscosity; PA1 (b) from 0.5% to 40% of the mixture of mono alkyl phenyl sulfonates of alkaline earth metals of the present invention; PA1 (c) from 0% to 20% of at least one ashless dispersant; PA1 (d) from 0% to 5% of at least one zinc dithiophosphate; PA1 (e) from 0% to 10% of at least one oxidation inhibitor; PA1 (f) from 0% to 1% of at least one foam inhibitor; and PA1 (g) from 0% to 20% of at least one viscosity index improver. PA1 (a) a major amount of an oil of lubricating viscosity; PA1 (b) from 0.5% to 40% of the mixture of mono alkyl phenyl sulfonates of alkaline earth metals of the present invention; PA1 (c) from 0% to 20% of at least one ashless dispersant; PA1 (d) from 0% to 5% of at least one zinc dithiophosphate; PA1 (e) from 0% to 10% of at least one oxidation inhibitor; PA1 (f) from 0% to 1% of at least one foam inhibitor; and PA1 (g) from 0% to 20% of at least one viscosity index improver.
It is easy to obtain a good dispersion in the medium of the alkaline earth base not fixed in the form of salt if the sulfonic acid is derived from a hydrocarbon obtained by alkylation of an aryl hydrocarbon with a branched olefin. It is difficult if the alkylation is effected with a linear olefin. It is particularly difficult for the alkylation of an aryl hydrocarbon where a high percentage of the alkylaryl hydrocarbon has the aryl substituent on positions 1 and 2 of the linear alkyl chain, due to the formation of a skin in the open air.
This poor dispersion is especially pronounced if the medium also contains a high proportion of sulfonate, that is if it corresponds to a low Base Number (between 3 and 60), hence to a low content of free lime and the absence of carbon dioxide and carbonate.
In fact, during the alkylation reaction with benzene or another aromatic or aryl hydrocarbon, 25 mole % of the alkylaryl hydrocarbon has the aryl substituent on positions 1 and 2 of the linear alkyl chain.
When prepared by the method described, for example in French Patent No. 2,564,830, this high proportion of alkyl aryl hydrocarbon having an aryl radical on position 1 or 2 of the linear alkyl chain results in a sulfonate that exhibits hygroscopic properties such that a superficial `skin` is formed. This `skin` makes this product unacceptable as an additive for lubricating oil.
Furthermore, the formation of this superficial skin is generally accompanied by a very low filtration rate, a high viscosity, a low incorporation of calcium, a deterioration of anti-rust performance, and an undesirable turbid appearance, or even sedimentation, when the sulfonate thus prepared is added at the rate of 10% by weight to a standard lubricating oil and stored for examination.
The Applicant has carried out chromatographic analyses to identify each of the different isomers differing by the position of the aryl radical on the carbon atom of the linear alkyl chain, and examined their respective influence on the properties of the corresponding alkyl aryl sulfonates of alkaline earth metals obtained from these different isomers.
The Applicant has thus discovered that he could overcome the aforementioned drawbacks, inasmuch as the mole % of the aryl hydrocarbon, other than benzene, having the aryl substituent on positions 1 or 2 of the linear alkyl chain was between 0 and 13%, and preferably between 5 and 11%, and more particularly between 7 and 10%.
This discovery was the subject of a French Patent Application filed Mar. 8, 1995 under No. 95 02,709 by the Applicant.
Yet the Applicant had not succeeded in obtaining satisfactory results when the aryl hydrocarbon was benzene, because, heretofore, he had never been able to prevent the formation of the skin with the use of this aromatic hydrocarbon, even if the hydrocarbon was alkylated with a very long chain linear mono olefin so that the mole % of the aryl hydrocarbon having the aryl substituent on positions 1 or 2 of the linear alkyl chain was between 0 and 13%, and preferably between 5 and 11%, and more particularly between 7 and 10%.
As a result of more intensive studies, the Applicant had discovered that the aforementioned drawbacks could be overcome by using a mixture of alkyl aryl sulfonates of superalkalinized alkaline earth metals comprising:
(i) dialkyl aryl sulfonates wherein both alkyl substituents are linear alkyl chains, of which the sum of the carbon atoms is from 16 to 40, or PA2 (ii) mono or polyalkyl aryl sulfonates wherein the alkyl substituent or substituents are branched chains, wherein the sum of the carbon atoms is from 15 to 48 carbon atoms. PA2 1) Phenol type phenolic) oxidation inhibitors: 4,4'-methylenebis (2,6-di-tert-butylphenol),4,4'-bis(2,6-di-tert-butylphenol), PA2 4,4'-bis(2-methyl-6-tert-butylphenol),2,2'-(methylenebis(4-methyl-6-tert-b utyl-phenol), PA2 4,4'-butylidenebis(3-methyl-6-tert-butylphenol), PA2 4,4'-isopropylidenebis(2,6-di-tert-butylphenol), PA2 2,2'-methylenebis(4-methyl-6-nonylphenol), PA2 2,2'-isobutylidene-bis(4,6-dimethylphenol), PA2 2,2'-methylenebis(4-methyl-6-cyclohexylphenol), PA2 2,6-di-tert-butyl4-methylphenol, 2,6-di-tert-butyl4-ethylphenol, PA2 2,4-dimethyl-6-tert-butyl-phenol, PA2 2,6-di-tert-.alpha.-dimethylamino-p-cresol, 2,6-di-tert-4(N.N' dimethylaminomethylphenol),4,4'-thiobis(2-methyl-6-tert-butylphenol), 2,2'-thiobis(4-methyl-6-tert-butylphenol), PA2 bis(3-methyl-4-hydroxy-5-tert-butylbenzyl)-sulfide, and bis (3,5-di-tert-butyl4-hydroxybenzyl). PA2 2) Diphenylamine type oxidation inhibitor: alkylated diphenylamine, phenyl-.alpha.-naphthylamine, and alkylated .alpha.-naphthylamine. PA2 3) Other types: metal dithiocarbamate (e.g., zinc dithiocarbamate), and methylenebis (dibutyidithiocarbamate). PA2 1) Nonionic polyoxyethylene surface active agents: polyoxyethylene lauryl ether, polyoxyethylene higher alcohol ether, polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenyl ether, polyoxyethylene octyl stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene sorbitol monostearate, polyoxyethylene sorbitol mono-oleate, and polyethylene glycol monooleate. PA2 2) Other compounds: stearic acid and other fatty acids, dicarboxilic acids, metal soaps, fatty acid amine salts, metal salts of heavy sulfonic acid, partial carboxylic acid ester of polyhydric alcohol, and phosphoric ester. PA2 (7) Multifunctional additives: sulfurized oxymolybdenum dithiocarbamate, sulfurized oxymolybdenum organo phosphoro dithioate, oxymolybdenum monoglyceride, oxymolybdenum diethylate amide, amine-molybdenum complex compound, and sulfur-containing molybdenym complex compound
This mixture of alkyl aryl sulfonates has a maximum of 10 mole % of the phenyl sulfonate radical of the alkaline earth metal fixed on position 1 or 2 of the linear alkyl chain. This mixture has no skin formation after three days of storage in an open jar at room temperature. It has good calcium incorporation, a low viscosity, good solubility, and good performances. This discovery was the subject of a French Patent Application filed Sep. 5, 1996 under No. 96 10,833 by the Applicant.
According to that process, the linear mono-alkyl phenyl sulfonates should have no more than 13% attachment in position 1 or 2. Such low levels of attachment in the 1 or 2 position is possible using a staged HF catalyst alkylation reaction (two reactors in serial; low molar excess of benzene in the first reactor, large molar excess in the second), but it is not possible if only one reactor is available.